REM
    REM --- Tiny BASIC Interpreter and Compiler Project
    REM --- Hunt the Wumpus Demonstration Game
    REM
    REM --- Released as Public Domain by Damian Gareth Walker 2019
    REM --- Created: 08-Aug-2019
    REM

    REM --- Variable List
    REM
    REM A - Bat 1 position
    REM B - Bat 2 position
    REM C - Player position
    REM D - Destination to move or shoot
    REM E - exit 1 from the current cave
    REM F - exit 2 from the current cave
    REM G - exit 3 from the current cave
    REM H - Hole 1 (bottomless pit) position
    REM I - Hole 2 (bottomless pit) position
    REM J - Randomised position for player or hazard
    REM K - origin location of arrow in motion (before L)
    REM L - previous location of arrow in motion
    REM M - menu option for move or shoot
    REM N - range for arrow shot
    REM P - parameter to the 'exits' routine
    REM Q - number of arrows in quiver
    REM R - random number
    REM S - random number generator seed
    REM W - Wumpus position

    REM --- Intialise the random number generator
    PRINT "Think of a number"
    INPUT S

    REM --- Initialise the player and hazard positions
    LET A=0
    LET B=0
    LET C=0
    LET H=0
    LET I=0
    LET W=0

    REM --- Fill the player's quiver
    LET Q=5

    REM --- Distribute the player and hazards across the map
    GOSUB 130
    LET A=J
    GOSUB 130
    LET B=J
    GOSUB 130
    LET C=J
    GOSUB 130
    LET H=J
    GOSUB 130
    LET I=J
    GOSUB 130
    LET W=J

    REM --- Introductory text
    PRINT "You enter the caves to Hunt the Wumpus!"

    REM --- Main Game Loop
 30 PRINT "You are in room ",C
    LET P=C
    GOSUB 200
    GOSUB 50
    PRINT "Exits are ",E,",",F,",",G
 35 PRINT "1:Move or 2:Shoot?"
    INPUT M
    IF M<1 THEN GOTO 35
    IF M>2 THEN GOTO 35
    IF M=1 THEN GOSUB 120
    IF M=2 THEN GOSUB 150
    GOTO 30

    REM --- Subroutine to check for hazards

    REM Has the player encountered a bat?
 50 IF C<>A THEN IF C<>B THEN GOTO 60
    PRINT "A bat swoops down and picks you up..."
    GOSUB 100
    PRINT "...and drops you down"
    LET P=C
    GOSUB 200

    REM Has the player fallen in a pit?
 60 IF C<>H THEN IF C<>I THEN GOTO 65
    PRINT "You fall down a bottomless hole into the abyss!"
    END

    REM Has the player startled the wumpus?
 65 IF C<>W THEN GOTO 70
    PRINT "You stumble upon the wumpus!"
    GOSUB 90
    PRINT "The wumpus runs away!"

    REM Is there a pit nearby?
 70 IF E<>H THEN IF F<>H THEN IF G<>H THEN GOTO 72
    GOTO 73
 72 IF E<>I THEN IF F<>I THEN IF G<>I THEN GOTO 75
 73 PRINT "You feel a cold wind blowing from a nearby cavern."

    REM Is the wumpus nearby?
 75 IF E<>W THEN IF F<>W THEN IF G<>W THEN GOTO 80
    PRINT "You smell something terrible nearby."

    REM Is there a bat nearby?
 80 IF E<>A THEN IF F<>A THEN IF G<>A THEN GOTO 82
    GOTO 83
 82 IF E<>B THEN IF F<>B THEN IF G<>B THEN GOTO 84
 83 PRINT "You hear a loud squeaking and a flapping of wings."
 84 RETURN

    REM --- Relocate the Wumpus
 90 GOSUB 140
    LET R=R-(R/4*4)
    IF R=1 THEN LET W=E
    IF R=2 THEN LET W=F
    IF R=3 THEN LET W=G
    IF W<>C THEN RETURN
    PRINT "The wumpus eats you!"
    END

    REM --- Relocate bat and player
100 GOSUB 140
    LET R=R-(R/4*4)
    IF R=0 THEN RETURN
    LET P=C
    GOSUB 200
    IF R=1 THEN LET D=E
    IF R=2 THEN LET D=F
    IF R=3 THEN LET D=G
    IF D<>A THEN IF D<>B THEN GOTO 110
    GOTO 100
110 PRINT "...moves you to room ",D,"..."
    IF A=C THEN LET A=D
    IF B=C THEN LET B=D
    LET C=D
    GOTO 100

    REM --- Subroutine to move
120 PRINT "Where?"
    INPUT D
    IF D<>E THEN IF D<>F THEN IF D<>G THEN GOTO 120
    LET C=D
    RETURN

    REM -- Find a random unoccupied position
130 GOSUB 140
    LET J=1+R-R/20*20
    IF J<>A THEN IF J<>B THEN IF J<>C THEN GOTO 134
    GOTO 130
134 IF J<>H THEN IF J<>I THEN IF J<>W THEN RETURN
    GOTO 130

    REM --- Random number generator
140 LET S=5*S+35
    LET S=S-S/4096*4096
    LET R=S
    RETURN

    REM --- Subroutine to shoot
150 PRINT "Shoot how far (1-5)?"
    INPUT N
    IF N<1 THEN GOTO 150
    IF N>5 THEN GOTO 150
    LET P=C
    LET L=0
160 GOSUB 200
    LET K=L
    LET L=P
    PRINT "Arrow is next to rooms ",E,",",F,",",G 
164 PRINT "Shoot where?"
    INPUT P
    IF P<>E THEN IF P<>F THEN IF P<>G THEN GOTO 180
    IF P=K THEN GOTO 185
    IF P=W THEN GOTO 195
    LET N=N-1
    IF N>0 THEN GOTO 160
    LET Q=Q-1
    PRINT "The arrow startles the wumpus."
    LET P=W
    GOSUB 200
    GOSUB 90
    IF Q=0 THEN GOTO 190
    PRINT "You have ",Q," arrows left."
    RETURN
180 PRINT "The arrow can't reach there."
    GOTO 164
185 PRINT "The arrow can't double back on itself."
    GOTO 164
190 PRINT "You used your last arrow!"
    PRINT "Your demise is now inevitable."
    END
195 PRINT "You hit the wumpus!"
    END

    REM --- Subroutine to set the exits
    REM Input: P - current position
    REM Outputs: E, F, G (exits)
200 IF P>=1 THEN IF P<=20 THEN GOTO 205
    PRINT "Illegal position ",P
    END
205 GOTO 200+10*((14+P)/10)

    REM --- Outer caves
210 LET E=P-1
    IF E=0 THEN LET E=5
    LET F=P+1
    IF F=6 THEN LET F=1
    LET G=4+2*P
    RETURN

    REM --- Middle caves
220 LET E=P-1
    IF E=5 THEN LET E=15
    LET F=P+1
    IF F=16 THEN LET F=6
    IF P/2*2<>P THEN LET G=13+P/2
    IF P/2*2=P THEN LET G=P/2-2
    RETURN

    REM --- Inner caves
230 LET E=P-1
    IF E=15 THEN LET E=20
    LET F=P+1
    IF F=21 THEN LET F=16
    LET G=2*P-25
    RETURN